This application claims priority under 35 U.S.C. xc2xa7xc2xa7119 and/or 365 to 0003426-4 filed in SWEDEN on Sep. 25, 2000; the entire content of which is hereby incorporated by reference.
The present invention relates to the field of radio communication and, in more particular, to a portable communication apparatus of the type having a display and at least one antenna.
Examples of a portable communication apparatus as set out above are a mobile telephone, a cordless telephone, a portable digital assistant, a communicator, a paging device, an electronic payment device, or a portable navigating device. Among these, the mobile or cellular telephone is currently believed to be the most prominent in terms of market penetration and sales volumes. Therefore, for the rest of this document, reference will be made to a mobile or cellular telephone for any commercially available mobile communications network, such as GSM, UMTS or D-AMPS. However, the invention is not limited to merely a mobile telephone. On the contrary, the invention is best defined by the appended independent patent claims.
Traditionally, older mobile telephones were only capable of normal speech communication between two users through a mobile communications network and, in many situations, a public switched telephone network. Historically, mobile telephones have often been provided with a monopole antenna mounted externally to the apparatus housing of the telephone. Rod antennas, whip antennas and helix antennas are some examples of such external monopole antennas.
However, as the size and weight of mobile telephones have continued to decrease, the above-described antennas have become less advantageous. Consequently, some contemporary mobile telephones are provided with built-in antennas in the form of a printed pattern of conductive material. Microstrip patch antennas and planar inverted F antennas (PIFA) are examples of such antennas. They are advantageous, compared to the above-described conventional antennas, in terms of small size and low weight. However, as mobile telephones become smaller and smaller, conventional microstrip patch antennas as well as conventional PIFA antennas are still too large to fit inside a miniaturized mobile telephone chassis. This is expected to be a problem particularly for new generations of mobile telephones, which will use multiple antennas for different purposes, such as cellular telecommunication, access to wireless LAN, satellite communication (GPS) and diversity.
Various approaches have been suggested in order to reduce the size of a built-in antenna. In WO 96/27219 a meandering inverted F antenna is proposed, which allows a reduction of the antenna size to about 40% of the size of a conventional PIFA antenna.
WO 00/03453 proposes a miniature printed spiral antenna adapted to be built into a mobile terminal. Antenna matching is achieved by a matching bridge positioned between a feeding pin and a grounded post. The size of this antenna is 20-30% of the size of a conventional PIFA antenna.
To summarize the above, a problem with modern mobile telephones and similar portable communication equipment is that the miniaturized apparatus size limits the surface area available for a built-in antenna. The problem is particularly pronounced for a mobile telephone with multiple antennas. Some future mobile telephones are believed to offer satellite navigation functionality (such as GPS) in addition to traditional cellular telecommunication and, possibly, wireless access to local area networks (LAN) as well as diversity functionality.
The problem of fitting a built-in GPS antenna in a miniaturized mobile telephone is accentuated by the fact that the GPS antenna needs some isolation from the cellular antenna. Moreover, GPS functionality requires a more directional antenna than a normal omni-directional cellular antenna. Additionally, since GPS operates at 1.57 GHz, the wavelength is about 21 cm. Therefore, a half-wave GPS antenna in open air will be about 10 cm in size.
The present invention seeks to remedy the problems set out above, when a miniaturized portable communication apparatus is to be provided with a built-in antenna, for which it is hard to find enough available surface area in the apparatus. More particularly, it is an object of the present invention to allow a miniaturized mobile telephone to include a fully operational GPS antenna, which will not interfere with the cellular antenna and which will not occupy any externally visible surface area of the mobile telephone.
The above objects have been achieved by an integrated display and antenna device having a multi-layer structure, where the display (preferably an LCD) is provided at an upper layer and a plane patch antenna element is attached behind the display as a lower layer. Preferably, the multi-layer structure will include a light-guiding layer adapted to illuminate the display layer, as well as a dielectric antenna substrate, upon which the patch antenna element is supported. The multi-layer structure will preferably also include an antenna feeding layer having a feeding pin, coupled to GPS radio circuitry in the mobile telephone, as well as a grounded matching post. Alternatively, the antenna feeding layer may comprise two feeding pins, which are connected in a one-to-two microstrip power divider configuration, so that the two feeding pins will have a phase difference of 90xc2x0, so as to obtain circular polarization.
Moreover, the dielectric substrate layer may comprise a dielectric framework in the form of a grid, wherein the dielectric constant may be varied depending on the material chosen for the dielectric framework as well as the grid density. This will allow the resonant frequency of the patch antenna element to be tuned to the appropriate frequency (e.g. the GPS frequency at 1.57 GHz).
These and other objects of the present invention will appear clearly from the following detailed disclosure of preferred and alternative embodiments, from the enclosed drawings as well as from the appended claims.
It should be emphasized that the term xe2x80x9ccomprises/comprisingxe2x80x9d when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.